Quote:
Originally Posted by SteelheadJones
Your project is an inspiration to a card carrying member of the electrically hopeless society like me. The form factor of that heater is great. Does it offer continuous hot water, or just 1.6 gallons at a time and then you have to wait for it to fill up again?
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No continuous hot water with this arrangement. Rather you have at most 1.6 gals of 176F water being mixed w ambient water via a mixing valve to prevent scalding. I would estimate about 1.2 Gals of "hot" water before it becomes warm and then goes to the ambient temperature of the supply water tank.
Heating 60F water to 90F with 200watts will take about 25 mins. Heating the 60F to 125F will take about 50 mins. This assumes the 200 watt element is actually receiving enough current to generate 200watts of energy. At 12.5 volts the draw would be 16 to 18 amps. That is pretty significant amount of draw for 50 mins after which you will have 1.6 gal of 125F water that will be diluted temperature wise as the ambient water is added to the water heater tank.
We have an IsoTemp 4 gal SPA15 electric water heater which comes stock with a 750w 120VAC heating element and a coolant heat exchanging loop. I modified this to add a 12VDC 217watt heating element. We do not use the coolant loop. I can run the 750w element on shore power or the inverter if the engine is running. The 12vdc element is used with either the engine running or under strong sun via the 360w solar panel. Using the 12vdc element draws 18 amps and without the solar input will cause the 480 amp AGM battery bank voltage to drop to 11.8vdc pretty quickly.
With AC input the 750w element raises the water temperature to 160F in about 1.3 hours. The 217w element takes about 4.5 hrs. The following link provides a time/volume/watts/temperature change calculator. it is enlightening.
https://bloglocation.com/art/water-h...e-energy-power